Heat exchangers are used to transfer thermal energy from one stream of fluid at a first, higher temperature to another stream of fluid at a second, lower temperature. Oftentimes such heat exchangers are used to remove waste heat from a process fluid such as oil, coolant, or the like by transferring that heat to a flow of cooler air directed to pass through the heat exchanger.
In certain applications, the process fluid to be cooled is also at an operating pressure that is substantially greater than the ambient atmospheric pressure of the heat exchanger's surroundings. As a result, it becomes necessary for the heat exchanger to be designed to withstand the pressure forces that result from the process fluid passing through the heat exchanger. This can become challenging, especially in cases where the heat exchanger is to be used in large systems and machinery such as, for example, construction equipment, agricultural machines, and the like. As the size of the machine or system increases, the flow rate of the process fluid also increases, necessitating larger heat exchangers to accommodate both the heat transfer requirements and the fluid flow rates. Such larger heat exchangers can have substantially large surface areas exposed to the pressure of the process fluid, especially in tank areas, and the force of the fluid pressure acting on these large surfaces can lead to destructive mechanical stresses in the heat exchanger structure.
An example of such a heat exchanger as known in the art is depicted in FIG. 1. The heat exchanger 101 is of a bar and plate construction, and can be used as, for example, an oil cooler for an off-highway vehicle such as an excavator, wheel loader, combine, etc. Oil to be cooled by the heat exchanger 101 travels through a plurality of channels provided within a heat exchanger core 102, those channels alternating with channels for cooling air that is directed in a cross-flow orientation to the oil through the core 102. Tanks 103 are provided at either end of the core 102 to direct the oil to and from the core 102, and inlet/outlet ports 106 are provided at each of the tanks 103 to fluidly couple the heat exchanger 101 to the oil circuit.
The tanks 103 must be sized to be large enough to evenly distribute the flow of oil to the individual channels. As a result, substantially large surface areas within the tank are exposed to the typically high pressure of the oil, and must be designed to be capable of withstanding such forces. A typical tank construction for such high-pressure applications includes an extruded tank section 104 with an arcuate (e.g. cylindrical) internal profile in order to evenly distribute the forces resulting from the pressure loading. Flat end caps 105 are welded to the ends of the extruded tank section 104 in order to close off the ends of the tank 103. Those flat end caps 105 must again be designed with a thickness that is suitable for withstanding the pressure forces imposed on them by the fluid in the tank 103. Such a tank construction can be more economical than a tooled cast tank for low-volume manufacturing.
Even when such heat exchangers have been designed with wall sections suitable for withstanding the elevated operating pressure of the intended application, the forces acting on the end caps can result in undesirable and damaging stresses in the remainder of the heat exchanger. Thus, there is still room for improvement.